Abstract:
Salt bodies, sharp velocity differences, and numerous reflections make imaging subsurface geology in offshore Sudan, which is part of the tectonically complex Red Sea Basin of Northeast Africa, extremely difficult. By applying Full Waveform Inversion (FWI) and sophisticated broadband seismic processing techniques to 2D marine seismic data obtained from Offshore Block 13, this work seeks to improve the resolution of subsurface features. After reformatting and geometry assignment, the processing methodology included thorough noise attenuation using Plane Wave Dip Filtering (PWDF) for linear noise and Time-Frequency Denoising (TFDN) for swell noise. The vertical resolution was improved, and lost frequency content was recovered with the successful removal of source and receiver ghosts through subsequent deghosting using the DUG Broad method. After that, designature techniques were used to recover the true wavelet shape and account for bubble effects. To suppress both shallow and deep-water multiples, Surface-Related Multiple Elimination (SRME) and High-Resolution Radon Transform were used in succession. An original model utilized in Pre-Stack Depth Migration (PSDM) was created by combining traditional semblance analysis and tomography with velocity model development. However, a second seismic line with more distinct salt geometry was chosen for FWI because of the constraints in imaging beneath salt formations. By decreasing the mismatch between the synthetic and observed data, FWI iteratively updated the velocity model, starting at a frequency of 6 Hz to prevent cycle skipping. Reflector continuity and seismic event location were greatly enhanced by the final FWI-refined model, especially over the unconformity and under the salt. The FWI-updated model was used to create the final PSDM stack, which improved subsurface resolution, geological structure delineation, and confidence in stratigraphic and structural interpretation. This integrated technique is crucial to assisting hydrocarbon exploration efforts in the Red Sea region and shows that integrating broadband processing with FWI is a potent strategy for addressing imaging issues in offshore basins influenced by salt.
